准东煤成灰过程中钠的迁移特性及形态变化

摘要

In order to study the Migration characteristics and morphological changes of sodium during ashing process of Zhundong coal, Zhundong coal samples from five coal mines were ashed at 575 ℃ and 815 ℃,meanwhile,the ignition temperature and burnout tempera-ture of the samples were analyzed through thermogravimetric experiment. The influence of ashing temperature on ash characteristics of Zhundong coal was investigated. The ash was characterized with X-ray fluorescence( XRF),X-ray diffraction( XRD)and scanning elec-tron microscope and energy dispersive spectrometry( SEM-EDS). FactSage was used to explain and forecast sodium migration characteris-tics during ashing process. The results showed that,the ignition temperature of five Zhundong coals was below 400℃,the burnout tempera-ture was below 500 ℃. The form and physicochemical properties of ash which were obtained at 575 ℃and 815 ℃ respectively had large differences. Compared with the sodium in ash gotten at 575 ℃,the sodium content decreased by 47. 67%,88. 89%,62. 45%,52. 48%, 85. 78% at 815 ℃. The sodium on the surface of ash decreased by 67. 52%,75. 70%,44. 87%,63. 71% and 90. 08%. The ashing tem-perature influenced not only the sodium content,but the form of sodium. When the ashing temperature was higher than 800 ℃,the ash showed adhesive phenomenon. At last,575℃ was determined finally as ashing temperature which ensured complete combustion of Zhundo-ng coal and reduced volatilization of sodium content.%为研究准东煤成灰过程中钠的迁移特性及形态变化，通过热重试验分析了5种准东煤的着火温度和燃烬温度，在575和815℃成灰温度下对5种准东煤进行灰化试验；重点研究了成灰温度对准东煤成灰特性的影响，采用X射线荧光光谱仪（ XRF）、X射线衍射仪（ XRD）、扫描电镜－能谱分析仪（ SEM－EDS）等方法对成灰理化特性进行了表征，最后采用化学热力学软件FactSage模拟了准东木垒煤灰化过程中钠的迁移特性。结果表明，5种准东煤的着火温度均低于400℃，燃烬温度均低于500℃。575和815℃成灰物质形态与理化特性差异明显，815℃时5种准东煤成灰中钠含量相比575℃分别降低了47.67%、88.89%、62.45%、52.48%和85.78%，成灰表面钠含量分别降低了67.52%、75.70%、44.87%、63.71%和90.08%。成灰温度不仅影响煤灰中钠含量，还影响钠的赋存形态，800℃以上高温灰中出现黏结现象。最终确定5种准东煤的成灰温度为575℃，既能保证煤样成灰完全，又能最大限度减少灰化过程中碱金属钠元素的损失。